The overaal objectives of this research project are to develop a refractory strain of mosquitoes to infection with microfilarial pathogen in a sightly susceptible species of the Aedes scutellaris group. Two approaches to this problem are being used: a) a genetic method of selection and introgressive hybridization by using species of the Ae. scutellaris complex which is refractory such as Ae. riversi, Ae. malayensis, and Ae. alcasidi and cross them with highly susceptible ones such as Ae. polynesiensis, Ae. cooki and Ae. tabu. The purpose of these crosses is to transfer refractory genes from closely related species to a susceptible one and thus to alter their vectorial capacity. If successful results will be achieved, the refractory Ae. polynesiensis strain will be used to alter natural populations of Ae. polynesiensis into refractory ones and break transmission of filarial pathogens.